Optimal conditions, kinetic model and Packed Bed Reactor system for biodegradation of Linear Alkylbenzene Sulfonate by AOS-15 microorganism
BACKGROUNG: Linear alkylbenzene sulfonate (LAS), an anionic surfactant, is the most widely used ingredient in synthetic detergents, and is thus released to the environment in large quantities. Effective methods of treatment which can degrade LAS are need of the hour. OBJECTIVE: The aim of the present study is to develop a bioreactor for complete degradation of LAS using immobilized cells of AOS-15 microorganism isolated from the wastewater treatment plant of Lion Corporation Limited (Thailand) and alginate-entrapped cells of AOS-15 were used for degradation of LAS in a Packed Bed Reactor (PBR). RESULT: The batch shake flask study showed the suitable condition of AOS-15 free cell to biodegrade 3 g/L LAS is 2.1 g cell mass. Moreover, we studied LAS initial concentration and pH on the degradation of LAS of free and calcium alginate immobilized cells. The results showed that LAS degradation was significantly improved using immobilized cells compared to that of free cells, where 2.1 g of immobilized cell at pH7 totally removed 100 ml of 3 g/L LAS within 48 hours. The efficiency of LAS degradation was further monitored in batches and continuous bioreactor experiments. The kinetics of biodegradation was optimized at the best conditions of free cell experiment. Simultaneously, kinetics equation of LAS biodegradation in batch at LAS concentration of 1.5-5 g/L is: Further, on Packed Bed Reactor (PBR) system, the immobilized microorganism was placed in the PBR column and the synthetic medium with LAS was pumped into it at 0.06 ml/minute. LAS could be degraded by AOS-15 microorganisms up to 80–96% in 80 hours of continuous study. CONCLUSION: The LAS biodegradation by AOS-15 microorganisms in a continuous flow system of PBR showed the efficiency of biodegradation. Our experiment showed that the PBR system had a high efficiency of LAS degradation, i.e., in 0–84 h, the biodegradation rate ranged from 80– 96%.